[xen staging] xen: Don't cast away const-ness in vcpu_show_registers()

[patchbot@xxxxxxx]

commit c3923b9f30ab5715fa28d922546586875d95ebde
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Dec 30 06:41:46 2024 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Mar 4 19:46:41 2025 +0000

    xen: Don't cast away const-ness in vcpu_show_registers()
    
    The final hunk is `(struct vcpu *)v` in disguise, expressed using a runtime
    pointer chase through memory and a technicality of the C type system to work
    around the fact that get_hvm_registers() strictly requires a mutable 
pointer.
    
    For anyone interested, this is one reason why C cannot optimise any reads
    across sequence points, even for a function purporting to take a const 
object.
    
    Anyway, have the function correctly state that it needs a mutable vcpu.  All
    callers have a mutable vCPU to hand, and it removes the runtime pointer 
chase
    in x86.
    
    Make one style adjustment in ARM while adjusting the parameter type.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/include/asm/domain.h | 2 +-
 xen/arch/arm/traps.c              | 3 ++-
 xen/arch/x86/include/asm/domain.h | 2 +-
 xen/arch/x86/x86_64/traps.c       | 4 ++--
 4 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/xen/arch/arm/include/asm/domain.h 
b/xen/arch/arm/include/asm/domain.h
index f1d72c6e48..50b6a4b009 100644
--- a/xen/arch/arm/include/asm/domain.h
+++ b/xen/arch/arm/include/asm/domain.h
@@ -243,7 +243,7 @@ struct arch_vcpu
 
 }  __cacheline_aligned;
 
-void vcpu_show_registers(const struct vcpu *v);
+void vcpu_show_registers(struct vcpu *v);
 void vcpu_switch_to_aarch64_mode(struct vcpu *v);
 
 /*
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 3071c38768..445e7378dd 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -964,9 +964,10 @@ void show_registers(const struct cpu_user_regs *regs)
     _show_registers(regs, &ctxt, guest_mode(regs), current);
 }
 
-void vcpu_show_registers(const struct vcpu *v)
+void vcpu_show_registers(struct vcpu *v)
 {
     struct reg_ctxt ctxt;
+
     ctxt.sctlr_el1 = v->arch.sctlr;
     ctxt.tcr_el1 = v->arch.ttbcr;
     ctxt.ttbr0_el1 = v->arch.ttbr0;
diff --git a/xen/arch/x86/include/asm/domain.h 
b/xen/arch/x86/include/asm/domain.h
index b79d6badd7..5fc1d1e5d0 100644
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -688,7 +688,7 @@ bool update_secondary_system_time(struct vcpu *v,
 void force_update_secondary_system_time(struct vcpu *v,
                                         struct vcpu_time_info *map);
 
-void vcpu_show_registers(const struct vcpu *v);
+void vcpu_show_registers(struct vcpu *v);
 
 static inline struct vcpu_guest_context *alloc_vcpu_guest_context(void)
 {
diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index 02fdb3637d..22d4db240b 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -170,7 +170,7 @@ void show_registers(const struct cpu_user_regs *regs)
     }
 }
 
-void vcpu_show_registers(const struct vcpu *v)
+void vcpu_show_registers(struct vcpu *v)
 {
     const struct cpu_user_regs *regs = &v->arch.user_regs;
     struct cpu_user_regs aux_regs;
@@ -180,7 +180,7 @@ void vcpu_show_registers(const struct vcpu *v)
     if ( is_hvm_vcpu(v) )
     {
         aux_regs = *regs;
-        get_hvm_registers(v->domain->vcpu[v->vcpu_id], &aux_regs, crs);
+        get_hvm_registers(v, &aux_regs, crs);
         regs = &aux_regs;
         context = CTXT_hvm_guest;
     }
--
generated by git-patchbot for /home/xen/git/xen.git#staging